Presently known vault door locking systems may be divided into three general categories, namely, electrical, electronic and mechanical. Each has its own advantages and disadvantages in a particular application. Usually, mechanically operated locking systems are limited in their use to small banks, offices and other places where electrical or electronic locking systems are considered too costly.
The present locking system, which operates on fluid pressure, is closely related to the mechanical locking systems but has many advantages thereover. One disadvantage of the mechanical combination lock is that it is not too difficult for an unauthorized person to determine the correct combination to unlock a door on which it is used. This can be done by utilizing a listening device on the lock to detect movement of the mechanical parts and thereby correctly align the combination pins so as to unlock the same. Also, a person skilled in the art can easily, by feel with his finger tips, accomplish the same result. Opening a combination type mechanical lock can also be accomplished by use of a drill. Another disadvantage of the mechanical type lock is that seizure of the mechanical parts can occur. A still further disadvantage of a mechanical lock is that, because of its wide spread use, numerous people have become familiar with their operation and security is becoming more difficult to maintain as time goes on. Because of this, places which employ mechanical combination locking systems are extensively utilizing television cameras, security guards, electric fences, alarm trip means and/or expensive microwave systems as further protection to what should be protected by the lock itself. The electrical back-up systems, however, can be rendered inoperative without affecting the mechanical lock and thus do not provide an integrated complementing protective system.
Electrical or electronic locking systems provide perhaps better security than mechanical combination locks but they are so complex the cost becomes prohibitive and thus their use is very limited.
Accordingly, it is a principal object of the present invention to provide a lock that operates in such a manner it is most difficult, if not impossible, to open without prior knowledge of the combination.
A further object of the invention is to provide a locking system in which the combination can be fairly simple or extremely complicated depending upon the amount of security that might be required. In the case of a complicated combination, a group of persons may share a part of the complete combination.
A still further object of the invention is to provide a locking system in which the combination cannot be discovered by use of listening devices.